Answer:
208.3
Step-by-step explanation:
Since the numbers are decreasing as multiples, its a geometric progression.
[tex]S_{n}=\frac{a(1-r^{n} )}{1-r} ; r\neq 1 \ and\ r \ is\ less\ than\ 1\\common\ ratio=\frac{20}{50}=\frac{2}{5}\\ S_{10}=\frac{125(1-(2/5)^{10} )}{1-(2/5)} \\=208.3[/tex]
